Dilution Lab
This lab will refine your laboratory skills, while you practice some useful and important laboratory techniques. When
faced with the need to design an experiment, an experimenter may require that the independent variable be diluted to
different concentrations prior to application to a test system. For example, if an experiment called for solutions of 0.10 M,
0.20 M, 0.30 M, and 0.40 M calcium chloride, and only a 1.0 M solution of calcium chloride could be found, a procedure
for diluting the 1.0 M “stock” solution would be required.
There is more than one procedure that one can follow to prepare a series of solutions of varying concentrations. In
this lab, you will complete a dilution using two different procedures, and compare the procedures. Throughout this lab you
will find the following equation helpful:
C1V1 = C2V2
Where: C1 = the initial concentration (the concentration you have)
V1 = the initial volume (the volume it takes) (this will usually be the unknown for which you will solve the equation)
C2 = the final concentration (the concentration you want)
V2 = the final volume (the volume you need)
Materials
 Safety Goggles
 Plastic droppers
 1000 ppm NaCl stock solution
 6 beakers of various sizes
 Distilled Water
 Conductivity Probe
 4 graduated cylinders of various sizes
 Vernier LabPro
 TI-83+ or TI-84 Graphing Calculator
Dilution Procedure #1 (your group may complete procedures 1 & 2 in any order)
In this procedure you will dilute the stock solution (1000 ppm NaCl), repeatedly, to make a series of solutions. The
concentrations you will make are 200 ppm, 150 ppm, 100 ppm, 50 ppm, and 25 ppm. You will then measure and record
the conductivity of each solution in a data table.
Always double check your calculations before beginning to make a solution!
1.
Complete all calculations for Dilution Procedure #1 as follows: Use the equation C 1V1 = C2V2 to calculate the amount
of 1000 ppm NaCl stock solution required to make 50 mL each of 200 ppm, 150 ppm, 100 ppm, 50 ppm, and 25 ppm
NaCl solutions.
2.
In an appropriately-sized beaker, obtain the total amount of 1000 ppm NaCl stock solution needed to complete
Dilution Procedure #1.
3.
Use graduated cylinders to prepare the NaCl solutions by adding the appropriate amount of 1000 ppm NaCl stock
solution to enough distilled water to make 50 mL of each solution.
4.
Use the procedure below to measure the conductivity of each solution. Record the conductivity of the solutions in a
data table labeled “Table 1: The Conductivity of Solutions Prepared by Procedure #1.”
Dilution Procedure #2 (your group may complete procedures 1 & 2 in any order)
In this procedure you will dilute the stock solution (1000 ppm NaCl), serially, to make the same series of solutions.
The concentrations you will make are the same as in Procedure #1 and you will again measure and record the
conductivity of each solution.
Always double check your calculations before beginning to make a solution!
1.
Use the equation C1V1 = C2V2 to calculate the amount of 1000 ppm NaCl stock solution required to make 150 mL of a
200 ppm NaCl solution.
2.
Use graduated cylinders to prepare the 200 ppm NaCl solution by adding the appropriate amount of 1000 ppm NaCl
stock solution to enough distilled water to make up 150 mL of the solution. Label the beaker.
3.
Use the equation C1V1 = C2V2 to calculate the amount of 200 ppm NaCl solution required to make 150 mL of a 150
ppm NaCl solution.
4.
Use graduated cylinders to prepare the 150 ppm NaCl solution by adding the appropriate amount of 200 ppm NaCl
solution to enough distilled water to make up 150 mL of the solution. Label the beaker.
5.
Use the equation C1V1 = C2V2 to calculate the amount of 150 ppm NaCl solution required to make 150 mL of a 100
ppm NaCl solution.
6.
Use graduated cylinders to prepare the 100 ppm NaCl solution by adding the appropriate amount of 150 ppm NaCl
solution to enough distilled water to make up 150 mL of the solution. Label the beaker.
7.
Use the equation C1V1 = C2V2 to calculate the amount of 100 ppm NaCl solution required to make 150 mL of a 50
ppm NaCl solution.
8.
Use graduated cylinders to prepare the 50 ppm NaCl solution by adding the appropriate amount of 100 ppm NaCl
solution to enough distilled water to make up 150 mL of the solution. Label the beaker.
9.
Use the equation C1V1 = C2V2 to calculate the amount of 50 ppm NaCl solution required to make 150 mL of a 25 ppm
NaCl solution.
10. Use graduated cylinders to prepare the 25 ppm NaCl solution by adding the appropriate amount of 50 ppm NaCl
solution to enough distilled water to make up 150 mL of the solution. Label the beaker.
11. Use the procedure below to measure the conductivity of each solution. Record the conductivity in a data table labeled
“Table 2: The Conductivity of Solutions Prepared by Procedure #2.”
Procedure for Using the Conductivity Probe
1. Set the switch on the Conductivity Probe box to 0-2000 µS (2000 µS = 1000 mg/L).
2. Plug the Conductivity Probe into Channel 1 of the LabPro interface. Use the link cable to connect the TI Graphing
Calculator to the interface. Firmly press in the cable ends.
3. Turn on the calculator and start the DATAMATE program. To obtain the DATAMATE program, press LINK on the
calculator then select RECEIVE and press TRANSFER on the LabPro. It will take a few minutes to transfer
DATAMATE to the calculator.
4. Set up the calculator and interface for the Conductivity Probe.
a. Select SETUP from the main screen.
b. Press ENTER to select CH 1.
c. Select CONDUCTIVITY from the SELECT SENSOR menu.
d. Select CONDUCT 1000 (MG/L) from the CONDUCTIVITY menu.
5. Set up the data-collection mode.
a. To select MODE, press
once and press ENTER .
b. Select SINGLE POINT from the SELECT MODE menu.
c. Select OK to return to the main screen.
6. Collect concentration data.
a. Place the tip of the electrode into a beaker with 100mL of the sample water you are testing. The hole near the tip
of the probe should be covered completely.
b. When the reading has stabilized, select START to begin sampling. Important: Leave the probe tip submerged
while data is being collected for the next 10 seconds.
c. After 10 seconds, the conductivity value will appear on the calculator screen. Record this value in your data table.
d. Press ENTER to return to the main screen.
e. Select START to repeat the measurement. Record this value in your data table.
f. Press ENTER to return to the main screen.
Data Analysis

Reminder: When you draw a graph for a laboratory assignment, be certain to utilize the extent of the graph paper in
each direction, title the graph, and label each axis with the quantity represented on it along with the units of
measurement in parentheses.

On a single graph, plot conductivity vs. concentration for both procedures using a different symbol and line style for
each procedure.

Graphically compare the two procedures of dilution by visually comparing the graphs of the two procedures.

Title the next section of your report “Discussion.” Write a one or two paragraph Discussion in which you fully
differentiate between the two methods (procedures) for diluting a solution. Explain which method you would prefer to
use if the accuracy of your dilutions is critically important, and why you would select that method. Identify the method
that you believe will introduce more sources of error into the design of an experiment and justify that choice of
methods.
Dilution Lab Grade Sheet
Name
/100 Table of Contents updated
/400 Calculations shown
/100 List of Materials
/500 Graph
/300 Procedures listed
/500 Discussion
/100 Data initialed and dated
/2000 Total
Dilution Lab Grade Sheet
Name
/100 Table of Contents updated
/400 Calculations shown
/100 List of Materials
/500 Graph
/300 Procedures listed
/500 Discussion
/100 Data initialed and dated
/2000 Total
Dilution Lab Grade Sheet
Name
/100 Table of Contents updated
/400 Calculations shown
/100 List of Materials
/500 Graph
/300 Procedures listed
/500 Discussion
/100 Data initialed and dated
/2000 Total
Dilution Lab Grade Sheet
Name
/100 Table of Contents updated
/400 Calculations shown
/100 List of Materials
/500 Graph
/300 Procedures listed
/500 Discussion
/100 Data initialed and dated
/2000 Total